An effort has been made to define missiology. It is the study of the salvation that God has provided for the world in Christ and through the Holy Spirit in the coming of this kingdom into this suffering and sinful world; it describes the ways in which this salvation has been realized in history through the planting of churches and the erection of the signs of the kingdom; it considers the best ways in which the salvation of God can be proclaimed, demonstrated and realized in the world and finally it is called to evaluate theologically the non-christian religions and ideologies.
From this definition the conclusion can be made that the discipline of missiology consists of the following fields of study: theology of missions, history of missions, theory and practice of missions and theology of religions and ideologies.
Missiology can be practised from a theosentric, a church centric or a cosmocentric viewpoint. My conclusion is that God, Church and world can only be understood in the correct relationship to each other if we describe it from the viewpoint of the kingdom. The kingly rule of Christ over church and world makes it possible to dissolve the polarization between spiritual and secular into the comprehensive kingdom which has to do with the whole man, the whole church and the whole world.
Text of inaugural address delivered on April 27, 1989 in the Dept of Science of Religion and Missiology